The ultimate aim of the proposed research is to provide sufficient information from structural studies to establish the molecular mechanism of the H ion-translocating ATPases. To establish the fundamental amino acid side chains at the active site of the F1-ATPase, inactivation studies are being carried out with affinity analogues and other reagents which react covalently with the functional residues. The use of radiolabelled reagents and peptide mapping by high performance liquid chromatography makes it possible to assess the specificity of these reagents. Once it is established that the inactivation by a particular reagent is associated with a single or a limited number of amino acid side chains, sequence analysis will then be performed to establish the location of the essential residue in the primary structure.